The most common and reliable guide I have found for brokering peace between the geth and the quarian is the following:

In order to achieve peace between the two races, you need to get 5 to
7 points. These points are based on your ME2 and ME3 decisions. If you
have 4 points or below, you cannot achieve peace.

-Rewrote the Heretics (0 points)

-Destroyed the Heretics (+2 points)

-Tali is NOT exiled (+2 points)

-Tali has been exiled/You did not do the Loyalty Mission (0 points)

-Resolved Legion/Tali conflict either using the Paragon or Renegade options (+1 point)

-N7 Mission: Save the Admiral on Rannoch in ME3 (+1 point)

-N7 Mission: Destroy Geth Squadron on Rannoch in ME3 (+1 point)

-Completed Legion's Mission in ME3 (or no peace)

Now, I imported an ME2 save where I destroyed the heretics(+2), Tali is exiled, I resolved the Tali/Legion conflict using a renegade option(+1), I saved the admiral on Rannoch(+1) and destroyed the geth squadron(+1). Of course I also did Legion's mission.

This gives me 5 points which is enough to get the option.

I know that I also need 4 bars of reputation...which I think I have. I have about 3.5 bars of renegade, then above this I have an additional bar of what I assume is paragon, as it has a harp symbol and is blue.

This should be 4.5 reputation in total.

From what I can tell I more than meet the options to successfully broker peace between the quarian and the geth, however, I don't even see the options. They are not greyed out; they don't appear at all.

3 Answers
3

There's actually two requirements you have to do in order to broker peace. The first is getting the 5 points.

SECOND objective is that the following requirements MUST be met:

Tali must be exonerated (not exiled) WITHOUT convicting her father. You must charm/intimidate the Admirals or rally the crowd (which requires that you let Veetor go with Tali in the prologue and keep Kal alive during Halestrom) To complete this.

You must resolve the Legion/Tali conflict WITHOUT losing ether of their loyalty.

Actually, no, that's not right at all. You're right about the Tali/Legion conflict, but the rest of the things you listed are not required. You get points for doing them, so it's more likely that you'll get the option if you do, but you don't have to.
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Ember QuillMay 9 '12 at 2:48

Near as I can tell, no one has a good or right answer to this. The clearest indication and closest thing I think to be right is that during ME2, there's a conversation in which you speak to one of the admirals and they thank you for helping Tali. One of the options is saying that you did it for Tali. Another is encouraging them to go to war. The third is telling them something along the lines of seeking peace. This is the closest thing to a "right" answer that I've heard. No one really has any idea though.

i think you need either very high renagade or very high paragon score to actually pull it off, this is what i did to make peace

saved the two quarians in ME2 (in the first and second mission you do with tali before she joins your team), rewrote heretics, tali not exiled, saved admiral, did the reaper hack thing, and had a very high paragon score